Vol, 7, No. 7, July 1968
NOTES 3457
of both metal and nitrogen through this layer appears to be slow. I n order to complete the reaction, the nitridation would have to be continued for an impracticably long period. This problem might be overcome by continuous pulverization during the reaction or by carrying out the reaction with the metal in the gaseous, molten, or dissolved state. From the kinetic standpoint, combination of the molten metal with nitrogen, atomized in an electric arc, would perhaps be the best Acknowledgment.-The authors wish to thank Lt. meth~d.~ Some nitrides of the transition metals have Larry Frankel for technical assistance in obtaining already been obtained by treatment of liquid amalgams nuclear magnetic resonance spectra in connection with with ammonia,'O but the products were obtained in the determination of magnetic moments. highly disperse state and were not easily separable from the large amounts of mercury present. For preparative purposes, i t is preferable to use solid amalgams having a higher content of rare earth. The solubility" of the rare earth metals in mercury is very small. CONTRIBUTION FROM THE LABORATORIUM FW "Amalgams" with a higher rare earth content are susFESTK~RPERPHYSIK, E.T.H., ZURICH,SWITZERLAND pensions of different solid intermetallic compounds in mercury. These compounds are of the type LnHg,, The Preparation of Rare Rarth where x = 1-4, and have a moderate thermal stability. l 2 Their decomposition temperatures are well below the Nitrides from Amalgams melting points of the rare earth metals. Therefore, the B Y B. MAGYAR thermal decomposition of the amalgams yields solid rare earths in a highly dispersed form, thus offering good conReceived January 19, 1968 ditions for direct union with nitrogen. The following scheme was found to yield stoichiometric rare earth Many transition and rare earth metal compounds nitrides have been examined as new ferromagnetic semiconductors, but this important property has so far been demonstrated conclusively only in some compounds of wherex = 1-4 and Ln = La, Pr, Nd, Gd, or Tm. Table europium(I1) l v 2 and chromium(II1) InvestigaI contains the stoichiometric ratio and the lattice contions of the rare earth nitrides have not been definitive, stants of some nitrides obtained by the amalgam since the samples which have been prepared either by method. The composition of the amalgam seemed to direct combination of the element^^-^ or by reaction of have no influence upon the composition of the obtained the hydride and nitrogen8 have contained amounts of nitride. There appreared to be little advantage in nitrogen to metal in less than the stoichiometric ratio. using a nitrogen-ammonia mixture for the nitridation The samples contained either unreacted metal or a secas the reaction with nitrogen alone was sufficiently ond anion, presumably 02-. If air is carefully excluded rapid. This method readily afforded mixed crystals of during preparation of the nitride, any oxygen present rare earth nitrides a t a relatively low temperature. must have preexisted in the metal as an impurity. This represents a considerable advantage over the more Such oxygen can probably not be removed by outgasusual method of heating the two nitrides together, resing the metal, since, a t the elevated temperatures requiring a high temperature, presumably owing to slow quired for outgassing, oxygen is chemically bound by diffusion in the nitride phase. The systems Gdl-,the metal. Since the oxygen content of commercially Pr,N and Gdl-,La,N were studied. The mutual solavailable metals is in the range 0.1-1.0 mol yo,products ubility of the nitrides was readily estimated from a plot with a nitrogen/metal ratio of 0.99 are to be expected. of the unit cell dimensions against the chemical compoL.ower ratios than this must be attributed to incomplete sition (see Figure 1). At 1000°, the PrN-rich phase reaction of the metal with nitrogen. The incomplete dissolved 46 mol % of GdN, whereas the GdN-rich reaction of the metal with nitrogen presumably occurs phase dissolved up to 7 mol yo of PrN only. Upon for kinetic reasons. During the reaction the metal nitridation, mixed amalgams of the composition Prl-,particles become coated with nitride, and the diffusion Gd,Hg, yielded two phases, both having the NaCl struc(1) B. T. Mattias, R. M. Bozarth, and J. H. Van Vleck, Phys. Reu. Lettevs, '7, 160 (1961). ture, when x had a value between 0.07 and 0.54. The ( 2 ) G. Busch, P. Junod, M. Risi, and 0. Vogt, Proceedings of the InterGd,,La,N system behaved similarly, where the solunational Confernence on Semiconductors, Exetter, 1962, p 729. (3) P. K . Bdtzer, €1. W. Lehmann, and M. Robhins, Phys. Rev. Letters, bility gap extended from x = 0.00 to x = 0.60. 16, 493 (1965).
reagents were mixed and allowed to react a t room temperature for specified lengths of time, usually 1-10 min. The presence of isocyanide is indicated by a white to blue color change in the detector tube." T h e yields of isocyanide can be semiquantitatively estimated from the intensity of the color. The lowest amount of methyl isocyanide detectable is approximately 0.1 pg. Analyses .-All elemental analyses were performed by the Analytical Research Department, Chemical Research Laboratory, Edgewood Arsenal, M d .
(4) I. Tsubokawa, J. Phys. SOG.Japan, 1 5 , 1664 (1960). (5) H. A. Eick, hT. C. Baenziger. and L. Eyring, J . A m . Chem. Soc., '78, 5887 (1956). (6) A. Iandelli, 2. Anovg. Allgem. Chem., 288, 85 (1956). (7) G. Busch, P. Junod, F. Levy, and 0. Vogt, Proceedings of the International Conference on Magnetism, Nottingham, England, 1964. p 472. (8) D. E. La Valle, J . Inoug. Nucl. Chem., 24, 930 (1862).
(9) R. J. Gamhino a n d J. J. Cuomo, J . Eleclrochem. Soc., 113 (4), 40 (1966). (10) P. Ettmayer, Thesis, Vienna, 1964. (11) A. F. Messing and 0. C. Dean, ORNL-2871, Oak Ridge National Laboratory, Oak Ridge, Tenn., June 1960. (12) W. Lugscheider, Thesis, Vienna, 1964.
1458 NOTRS TABLE I Method of prepn of LnHg, x N/Ln ( + 0 00;) a0 (=to 001), A
PrN
NdN
A4 1 26 0 995 5 169
A 2 09 0 970 5 131
GdN
B 20 0 0 998 4 985
TmN
B 10 0 0 990 4 813
a, (A) 5.30
5.25
5.20
5.15
560
Acknowledgment.-The author is indebted to Professor G. Busch, director of the Laboratory for Solid State Physics, for his continued interest and to the "Verein zur Forderung der Festktjrperphysik ail der E.T.H." for financial support of this work.
5.05
5.00
0.2
Figure 1.-Mutual
0.4
0.6
0.8
solubility in the systems Gdl-,La,N Gdl-,Pr,N at 1000".
and
Experimental Section All manipulations were carried out under nitrogen or argon. (1) Preparation of Amalgams. Method A.-The dehydrated chloride was dissolved in methanol and electrolyzed with a graphite anode and a mercury ~ a t h o d e . ' ~Electrolysis was carried out in a vessel provided with ground-glass joints to permit introduction of a graphite anode (diameter 12 m m ) , a stirrer, a combined inlet and outlet for nitrogen, a water jacket, and a tap on the bottom. A voltage of about 40 5: was required t o maintain a current of 1-2 A, depending upon the distance between the anode and cathode (10-20 mm), the concentration of the rare earth chloride (half-saturated), and the temperature (about 20"). Owing t o the large surface area of t h e cathode, a total current of 1 A corresponded t o a density of 0.04 A/cm2. T h e electrolysis was stopped after 20-40 hr, and the amalgam obtained was run off into a two-bulb vessel. Any electrolyte carried with the amalgam was washed out with methanol under nitrogen. This vessel was then evacuated and sealed. T h e excess of mercury was then distilled from bulb 1 into bulb 2 and finally t h e vessel was sealed between the two bulbs. T h e composition of the amalgam obtained in bulb 1 depended upon the temperature a t which the mercury was distilled (200-300" ). Method B.-The amalgams of the rare earths were obtained by heating the metal (or metals for mixed nitrides) a t 300-350O in a sealed glass tube with 20-30 times its weight of mercury. This a t the same time achieved some purification of t h e metal, since t h e oxidation products were lighter than mercury and separated out a t the surface of the amalgam. T h e amalgam was obtained as a thick pulpy solid and could be nitrided directly. ( 2 ) Nitridation.-For the preparation of t h e nitride, the amalgam was placed in two molybdenum boats. T h e first of these, containing about one-fifth of the total amalgam, was used (13) H.
for further purification of the nitrogen, since the rare earth nitride formed from the amalgam was a very good absorbent for traces of oxygen. T h e boats were placed in a silica tube and heated in a stream of purified nitrogen in steps, a s follows: 2-3 hr a t 340", 2-3 hr at 600",12-15 hr at 700", and 1-5 hr a t 1000". 'The formation of the nitride is complete a t 700", but the final heating period is necessary t o increasc the particle size sufficiently in order to obtain sharp reflections in the X-ray powder diagrams. The use of rubber and plastic tubing for the nitrogen line was avoided because of their pernieability to moisture. All connections were made from glass tubes, with spherical joints included at suitable positions to maintain flexibility. ( 3 ) Analyses.-Analyses for the rare earths and nitrogen were carried out by complexometric and Kjeldahl assays, respectively, after dissolution of the nitride in 1 X hydrochloric acid. Owing t o the violence of t h e reaction, especially with nitrides not annealed a t high temperatures (1200"), the rate of dissolution in acid had to be carefully controlled to prevent loss of amnionia. This was conveniently accomplished by sealing a weighed amount of nitride in a glass bulb, fitted with a side arm drawn o u t into a capillary. For digestion, the capillary was broken, and when the dark nitride had become light in color owing t o conversion into LnCla ,x€IIO and Ln(OH)3.rH,0, the bulb was broken completely, anti the flask was closed until dissolution was complete.
S.Booth, I v o r g . Sw., 1, 15 (1039)
CONTRIBUTIOX FROM THE DEPBRTMEUT O F CHEMICAL TECHNOLOGY, FACULTY O F ENGINEERISG, OSAKAUNIVERSITY, MIYAKOJIMA-KU, OSAKA,JAPAN
Chlorovinylation of Palladium BY TOSHIHIDE 'I;UKATVA A S D SIIIGERU TsUTsunu
Receieed Ja?tuary 22, 1968
Recently some organopalladium compounds from the reactions of palladium(I1) salts with unsaturated organics have been investigated by several workers. -5 For example, Anderson and Burreson have prepared acetoxy palladium(I1) olefin adducts. Cope and coworkers have found palladium(I1) halides to react with azobenzenes to give I2 and with allylic amines to give 11.3
I
I1
(1) C. B. Anderson and B. J. Burreson, J . Ovgnnomelal. Chetn. (Amsterdam), 7, 181 (1967). ( 2 ) A. C. Cope and R. W. Siekman, J . A m . Chem. Soc., 87, 3272 (1965). (3) A. C. Cope, J. M. Klienian, and E. C. Friedrich, i b i d , , 89, 287 (1967). (4) J. Tsuji and H. Takahashi, ibid., 87, 3275 (1965). ( 5 ) J. K. Stille and li. A. Morgan, ibid., 88,Z13.5 (1960).
